package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }


    //返回值不确定的时候，采用泛型
    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type,
                                         Function<ID,R> dbFallback, Long time, TimeUnit unit){
        String  key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (!StrUtil.isBlank(json)) {
            //3.存在，直接返回
            //Shop shop = JSONUtil.toBean(json, Shop.class);
            return JSONUtil.toBean(json, type);
        }

        //判断命中的是否是空值
        //!StrUtil.isBlank(shopJson)对于true的要求很高，所以需要二次判断是否为null
        if (json != null) {
            //返回一个错误信息
            return null;
        }

        //4.不存在，根据iD查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis  //返回错误信息
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);

            return null;
        }

        //6.存在，写入redis
        //设置超时的时间
        /*stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),
                CACHE_SHOP_TTL, TimeUnit.MINUTES);*/
        this.set(key, r, time, unit);
        //7.返回

        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit){
        String  key = CACHE_SHOP_KEY + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            return null;
        }

        //4. 命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject)redisData.getData();
        R r = JSONUtil.toBean(data, type);

        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期，直接返回店铺信息
            return r;
        }


        //5.2 已过期，需要缓存重建

        //6. 缓存重建

        //6.1 获取互斥锁
        //lockshop
        String lockKey = LOCK_SHOP_KEY + id;
        Boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取锁成功
        if (isLock) {
            // TODO 6.3 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                //重建缓存
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                    //this.saveShop2Redis(id,20L);

                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }

            });
        }
        //6.4.返回过期的店铺信息
        return r;
    }



    private boolean tryLock(String key){
        //只有当 key 不存在时，才设置值;;单位是秒，即 10 秒
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //flag有可能不存在
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }




}
